A Low Temperature Poly-Silicon-Thin Film Transistor (LTPS-TFT) display have the advantages of high resolution, fast response, high brightness, high aperture ratio and high electron mobility.
Currently, a low-temperature poly-silicon thin film transistor includes an active layer, a gate insulating layer, a gate electrode, a source electrode and a drain electrode which are disposed on a substrate. The active layer includes a source region, a drain region, and a channel region between the source region and the drain region. In order to avoid the channel region of the active layer being irradiated with light to generate leakage current and the electrical performance of the poly-silicon thin film transistor being affected, a metal light-shielding layer needs to be provided at a position corresponding to the channel region.
The active layer is obtained by performing an ion implantation process on a poly-silicon layer. The poly-silicon layer is generally formed by means of: forming an amorphous silicon thin film on a substrate, then converting the amorphous silicon thin film into a poly-silicon thin film by an excimer laser annealing method, and then the poly-silicon thin film is patterned by a patterning process to form a poly-silicon layer having a specific pattern. Alternatively, an amorphous silicon thin film may be formed on a substrate firstly, and a specific pattern is formed through a patterning process, then the amorphous silicon is converted into the poly-silicon by an excimer laser annealing method to form a poly-silicon layer.
However, due to the existence of the metal light-shielding layer, the heat dissipation rates of the source region and the drain region are quite slower than the heat dissipation rate of the channel region. When the excimer laser annealing converts the amorphous silicon into the poly-silicon, the channel region has crystallized, but the temperature of the source region and the drain region has not reached the crystallization temperature yet, resulting in smaller sizes of the crystal particles, poor uniformity of the crystal particles and poor crystal quality, and thus limiting the improvement of the electrical performance of the thin film transistor device.